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My new QMX+ #QMXplus

 

Just wanted to say that the QMX+ was a pleasure to build and, now that I've actually read the operations manual, it seems to be working as advertised!? With the GPS finally syncing up.
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My power is pretty typical I guess but I am a bit surprised that the the 20 and 17 are so much less than the 15 meter output.? Built for 12V
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160? -? ?5.6
80? ? -? ?5.6
60? ? -? ?4.8
40? ? -? ?4.8
30? ? -? ?5.0
20? ? -? ?3.8
17? ? ?-? 3.0
15? ? ?-? 5.2
12? ? ?-? 3.1
10? ? ?-? 3.8
6? ? ? ?-? 2.5
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Everything seems to be as advertised with no issues when following instructions.? HI
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If any one has found a way to get 20 and 17 up a bit i would be interested.? seems they should be as good as 30 and 15!
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Anyway very nice project.? Hats off to Hans for another fun radio.
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Mark N5MF
 

Hey Mark,
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Congratulations on your successful build!
My QMX+ also produced very silimlar output. Yours being slightly better results.
I built mine for 9v and posted my results a few days back. The general consensus seems to be that those are typical expected values.
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Cheers?
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Mel. M0KMD.
 

Ok thanks.? I figured as much.? Not a big deal but it is curious.
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Mark
 

Here is my post for reference?
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Mel.M0KMD
 

Mark,
?I have had the same problem trying to get 20, 17, & 15 m to peak up in power. Whenever you get one band up, the others are down. I don't think there's a good solution, but it's well under 1/2 S unit down, so I don't think it's a big problem. Be nice if there was an extra LPF so you only have to get 2 bands with each LPF.?
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73, Dan? NM3A
 

Agreed.? I think making a option for say 160-20 of 40-10m or 6m would be nice.? Then maybe ea. filter only has to cover 2 bands
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Mark N5MF
 

On Sat, Feb 22, 2025 at 09:12 AM, Mark Flavin wrote:
option for say 160-20 of 40-10m or 6m would be nice.? Then maybe ea. filter only has to cover 2 bands
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You can do this yourself by disabling the unwanted bands in the band configuration screen, then modify the filters and filter selections to be specific to the bands you want.
 

Could take the QMX+, redesign T501 and the LPF"s for CMCD with the tank placed out beyond T501.
It's preferable to have the tank right across the BS170 drains so T501 only needs to deal with the fundamental,?
but that makes band switching much more problematic.
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We have six LPF's in the QMX+.? Let's assume we shoot for a high enough Q that we need
to separate the CW and Phone parts of the 80m band.? So we might choose to peak those
six LPF slots (now resonant CMCD style output networks) for 80m, 75m, 40m, 20m 15m 10m.
That's all I could hope for in a $125 CW/Digital/SSB transceiver.
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It might be possible to still hit the WARC bands at reduced power.
Or you blow a second $125 for a QMX+ tuned to a few different bands.
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Jerry, KE7ER
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On Sat, Feb 22, 2025 at 09:27 AM, Stan Dye wrote:

On Sat, Feb 22, 2025 at 09:12 AM, Mark Flavin wrote:
option for say 160-20 of 40-10m or 6m would be nice.? Then maybe ea. filter only has to cover 2 bands
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You can do this yourself by disabling the unwanted bands in the band configuration screen, then modify the filters and filter selections to be specific to the bands you want.
 

Ill have to look into that. Thanks
 

That is another great idea.?
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Mark
 

T501 can be left as is, but I don't think we can use the primary center tap when going for CMCD.
Need two L502's to power the two sets of BS170 drains.
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From ?
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And this brings us to current-switching class D amplifiers. These actually?need?separate RF chokes that conduct a constant current over the RF cycle, and they?need?the drains?being completely decoupled from each other! So, using current-mode class D turns a very difficult design problem into a very easily implemented design feature!
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Jerry, KE7ER
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On Sat, Feb 22, 2025 at 10:33 AM, Jerry Gaffke wrote:

Could take the QMX+, redesign T501 and the LPF"s for CMCD with the tank placed out beyond T501.
 

Stan,
Absolutely you can eliminate 6 m and put 20 m (or 15 m) by itself. I was more thinking Hans could add one more LPF space so you wouldn't have to eliminate a band. There certainly is PCB real estate to do that. However, I am not that worried about it. I am perfectly happy the way it is. A half (or less) S unit down is NBD. In fact, I often deliberately run my 12 V rigs at 9-10 V anyway.?
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73, Dan? NM3A
 

Good point

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